audiosettings: add helper service to set ALSA defaults on RPI

scriptmodules/supplementary/audiosettings.sh

@@ -159,6 +159,36 @@ function _bcm2835_alsa_internal_audiosettings() {
     fi
 }
 
+# Adds a service to generate the ALSA configuration on HDMI 0 for a vc4-hdmi device (RPI configured with 'vc4-kms-v3d').
+# The service will disable itself afterwards, but can be enabled if re-running the configuration is desired.
+# If the RetroPie ALSA configuration is found, the service will not overwrite it.
+function alsa_defaults_service_audiosettings() {
+    local service="retropie-alsa-config.service"
+
+    mkdir -p "$md_inst"
+    cp -f "$md_data/alsa-defaults.sh" "$md_inst"
+    cat << EOF > "/usr/lib/systemd/system/$service"
+[Unit]
+Description=Configure ALSA default card on HDMI 0
+ConditionPathExists=!/etc/alsa/conf.d/99-retropie.conf
+Before=getty.target
+After=sound.target
+
+[Service]
+Type=oneshot
+TimeoutSec=120
+ExecStart=$md_inst/alsa-defaults.sh
+ExecStartPost=/usr/bin/systemctl disable $service
+
+[Install]
+WantedBy=multi-user.target
+EOF
+    # remove the RetroPie ALSA config file so it's created on next boot by the service
+    rm -f /etc/alsa/conf.d/99-retropie.conf
+    systemctl -q enable $service
+    printMsgs "console" "Installed the ALSA configuration service ($service)"
+
+}
 # configure the default ALSA soundcard based on chosen card index and type
 function _asoundrc_save_audiosettings() {
     [[ -z "$1" ]] && return

scriptmodules/supplementary/audiosettings/alsa-defaults.sh

@@ -0,0 +1,61 @@
+#!/bin/sh
+
+# Sets the default ALSA audio card to the 1st vc4-hdmi device found
+# The ALSA configuration is written to '/etc/alsa/conf.d/99-retropie.conf'
+
+CONF_FILE=/etc/alsa/conf.d/99-retropie.conf
+
+# test if we don't already have the audio configured
+if [ -f "$CONF_FILE" ]; then
+    echo RetroPie audio card configuration already present, skipping configuration
+    exit 0
+fi
+
+# test if we have any `vc4-hdmi` cards present, otherwise exit
+card_index="$(grep vc4hdmi /proc/asound/cards | cut -d' ' -f 2 | head -n1)"
+card_name="$(cat /proc/asound/card"${card_index}"/id)"
+if [ -z "$card_index" ]; then
+    echo No vc4-hdmi audio devices present, skipping configuration
+fi
+
+echo "Found a vc4-hdmi sound card on slot $card_index, configuring it"
+
+tmpfile="$(mktemp)"
+cat << EOF > "$tmpfile"
+pcm.hdmi${card_index} {
+  type asym
+  playback.pcm {
+    type plug
+    slave.pcm "hdmi:${card_name}"
+  }
+}
+ctl.!default {
+  type hw
+  card $card_index
+}
+pcm.softvolume {
+    type           softvol
+    slave.pcm      "hdmi${card_index}"
+    control.name  "HDMI Playback Volume"
+    control.card  ${card_index}
+}
+
+pcm.softmute {
+    type softvol
+    slave.pcm "softvolume"
+    control.name "HDMI Playback Switch"
+    control.card ${card_index}
+    resolution 2
+}
+
+pcm.!default {
+    type plug
+    slave.pcm "softmute"
+}
+EOF
+mv -f "$tmpfile" "$CONF_FILE" || {
+    echo "Failed to save configuration file $CONF_FILE!"
+    exit 1
+}
+chmod 0644 "$CONF_FILE"
+echo "ALSA configuration saved in $CONF_FILE"